Odor-controlling compositions and articles

ABSTRACT

Zeolites having &#34;intermediate&#34; SiO 2  /AlO 2  ratios are used to control odors. The intermediate zeolites find use in catamenials, diapers, pantiliners, bandages, and the like, where control of odors associated with bodily fluids is desired. Combinations of intermediate zeolites with other odor-controlling materials are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 08/028,646, filed on Mar.4, 1993, which is continuation of application Ser. No. 07/914,486, filedon Jul. 15, 1992, now abandoned, which is a continuation of applicationSer. No. 07/714,111, filed on Jun. 11, 1991, now abandoned, which is acontinaution-in-part of application Ser. No. 07/478,802, filed on Feb.12, 1990, now abandoned.

TECHNICAL FIELD

The present invention relates to odor-controlling agents which areespecially useful in articles such as catamenials, diapers, bandages,adult incontinence garments, and the like. The odor-controlling agentsherein are designed to combat a broad spectrum of odoriferous materials,including sour "ammonia-type" odors.

BACKGROUND OF THE INVENTION

A wide variety of absorbent structures designed not only to be efficientfor the absorption of body fluids such as blood, urine, menses, and thelike, but also to be sanitary and comfortable in-use are known in theliterature. Disposable products of this type generally comprise somesort of fluid-permeable topsheet material, an absorbent core, and afluid-impermeable backsheet material. Various shapes, sizes andthicknesses of such articles have been explored in an attempt to maketheir use more comfortable and convenient.

One particular aspect of sanitary products which has been underinvestigation for many years is that of odor control. Many body fluidshave an unpleasant odor, or develop such odors when in contact with airand/or bacteria for prolonged periods. The literature is replete withreferences relating to odor control in products such as diapers andcatamenials.

Various odor-controlling agents have been disclosed in the literature.In particular, certain zeolitic materials are becoming known for theirodor-controlling properties. Zeolitic materials are generally quitesafe, and while they do effectively control many odors associated withbody fluids, it has been determined that, unfortunately, they do notprovide optimal control for ammonia odor and similar odors, presumablyassociated with short-chain amines and/or urea. This is particularlytrue of the so-called "high ratio" (SiO₂ :AlO₂) ) odor-controllingzeolites.

It has now been determined that certain "intermediate ratio" (SiO₂:AlO₂) zeolites are quite effective for adsorbing amine-type odors.

Accordingly, the present invention provides a means for safely andeffectively overcoming the deficiencies in the art-disclosed "highratio" zeolitic odor-controlling agents by replacing them with"intermediate ratio" zeolites, or by using both types in combination.These and other advantages associated with the present invention will beseen from the disclosure, hereinafter.

BACKGROUND ART

The patent literature contains a considerable number of referencesrelating to odor control in sanitary products such as diapers, bandagesand catamenials. The following are illustrative.

EPO Patent Application 0304952 (published Mar. 1, 1989, U.S. priorityAug. 28, 1987), relates to a swellable polymer coated on a web ortissue, and with a deodorant powder, for use in fluid absorbentstructures such as sanitary napkins.

U.S. Pat. No. 4,385,632 (May 31, 1983) by S. O. Odelh oassigned toLandstingens Ink opscentral teaches copper odor control agents used onthe surface of absorbent articles.

U.S. Pat. No. 3,804,094 (Apr. 16, 1974) by K. Dossou, M. Gascon, G.Manoussos, assigned to L'Oreal Fr teaches a periodic acid odor controlagent used on the surface of an absorbent article.

U.S. Pat. No. 4,525,410 (Jun. 25, 1985) by Z. Hagiwara, H. Ohki, S.Hoshino, S. Nohara, S. Ida, K. Tagawa, assigned to Kanebo, Ltd. andKanto Chemical Co., Inc. teaches zeolite particles (doped withbactericidal cations) assertedly stably held in a fibrous web byincorporating some portion of meltable fibers in the web, and applyingheat; said to be useful as the "outside cover layer" in, e.g., "generalsanitary goods".

Japanese J63224734-A (88.09.19) Priority 87JP-058738 (87.03.16)J63224734 ASK KK relates to a paper comprising a powder or fiberobtained by grinding sepiolite, said paper having deodorizing capacity.

Japanese J63242261-A (88.10.07) 87JP-076111 J63242261 ASK KK relates toan odor-absorbing mat with sepiolite powder, a nonwoven fabric layer,and what appears to be a sheet to which the sepiolite is attached byadhesive. U.S. Pat. No. 2,690,415 (Sep. 28, 1954) by F. A. Shulerteaches particles of odor-absorbing materials uniformly affixed at theinterstices of a permeable web by adhesive to provide an odor absorbentmedium for, e.g., catamenials. Particulate carbon, silica gel andactivated alumina are noted. Shifting/displacement of the particulatesis assertedly avoided and the sheet is flexible. U.S. Pat. No. 3,093,546(Jun. 11, 1963) by R. L. Atkinson, teaches halogenated diphenyl methanederivatives "advantageously placed on the surface of a catamenialdressing" to "obtain prompt deodorizing activity".

Japanese J54141857 (J87019865) teaches the manufacture of powder(including zeolites) sheets by laminating the powder between a first andsecond sheet. Powders include activated carbon, zeolite, etc. Theabstract indicates use in catamenials or deodorizing materials.

BE-815446 (Abstract) teaches sanitary towels with chlorophyll crystalsor activated carbon, either in the absorbent layer, on the surface, or(per abstract) between.

ABSCENTS (odor-control molecular sieve from Union Carbide)--Use indiapers and catamenials is specifically noted in Union Carbide brochure(A. J. Gioffre 1988). The brochure indicates that UC's market researchshows potential benefits in such products. U.S. Pat. Nos. 4,795,482 and4,826,497, relate to ABSCENTS used as an odor-controlling agent,generally, and in sanitary products, in particular.

Various other patents relating to various absorbent gelling materials,topsheets, diaper and catamenial designs, and the like, are listed inthe Detailed Description and Examples, hereinafter. All documents citedin this specification are incorporated herein by reference.

SUMMARY OF THE INVENTION

The present invention relates to a method for decreasing odorsassociated with bodily fluids such as menses, vaginal discharges andurine, and the like, comprising contacting said fluids with anodor-controlling amount of an intermediate ratio SiO₂ AlO₂ zeolite.Zeolites of this "intermediate" type are those wherein the SiO₂ AlO₂ratio of said zeolite is less than about 10. The zeolite is preferablyin the protonic, sodium, potassium, ammonium or alkylammonium form, andis most preferably free of heavy metal cations. The method is especiallyuseful when the bodily fluid comprises menses and other vaginaldischarges.

In an optional mode, the method herein can be one wherein theintermediate ratio SiO₂ AlO₂ zeolite is used in combination with a highratio SiO₂ AlO₂ zeolite. Alternatively, the intermediate zeolite is usedin combination with activated carbon; or, the "intermediate" and "high"zeolites can both be used in combination and conjointly with activatedcarbon.

The invention also encompasses articles of manufacture, comprising afluid-absorbing pad, or the like, said pad comprising one or morewater-wettable fluid-absorbing materials and an odor-controlling amount,generally at least about 0.2 g., typically 0.24 g. to 0.4 g. of anintermediate ratio (said ratio being preferably about 2 to about 10)SiO₂ /AlO₂ zeolite. More zeolite can be used, as desired. Typically,such pads comprise at least 0.3 g of said zeolite. Such pads find useespecially as sanitary napkins or pantiliners. Preferably, the padscontain a polyacrylate or starch-acrylate absorbent gelling material,which not only absorbs fluid but also helps control amine-type odors.

The invention thus provides disposable diapers, sanitary napkins,pantiliners, and the like, wherein said fluid-absorbing pad isinterposed between a fluid-permeable topsheet and a fluidimpermeablebacksheet. In an alternate mode, the zeolite can be present in thetopsheet. Such articles can additionally comprise a high ratio SiO₂/AlO₂ zeolite, activated carbon, or mixtures thereof. Sanitary napkinsare an especially preferred article, herein.

All percentages, ranges and ratios herein are by weight, unlessotherwise specified.

DETAILED DESCRIPTION

The compositions and methods for controlling odors in the manner of thisinvention involve the use of zeolitic-type materials, as described morefully hereinafter.

The articles which employ said zeolitic odor-control technology can beprepared using constituents that are otherwise very well-known incurrent commercial practice, and reference can be made to the variouspatents mentioned herein and to the general sanitary products patentliterature and trade catalogues for such items. Such items typicallycomprise an absorbent "core" interposed between a "topsheet" and a"backsheet". Likewise, methods and apparatus for assembling disposablediapers, catamenials, bandages, and the like are known from patents andengineering literature.

While the constituents used in the assembly of catamenials, disposablediapers, and the like, are well-known, the following may be mentioned byway of example. It is to be understood that the present inventionresides in the novel assemblage of such items, or their equivalents,into the odor-controlling absorbent materials and structures disclosedherein, rather than in the constituents per se.

I. Zeolite Odor-Controlling Agent--The manufacture of zeolite materialsof the type used in the practice of this invention is well-known, andreference can be made to the voluminous literature for typical syntheticprocedures.

In order to assist the formulator and user of the compositions, articlesand methods of this invention (but not by way of limitation), attentionis directed to the synthetic procedures described in the followingreference texts: ZEOLITE SYNTHESIS, ACS Symposium Series 398, Eds. M. L.Occelli and H. E. Robson (1989) pages 2-7; ZEOLITE MOLECULAR SIEVES,Structure, Chemistry and Use, by D. W. Breck, John Wiley & Sons (1974)pages 245-250, 313-314 and 348-352; MODERN APPLICATIONS OF MOLECULARSIEVE ZEOLITES, Ph.D. Dissertation of S. M. Kuznicki, U. of Utah (1980),available from University Microfilms International, Ann Arbor, Michigan,pages 2-8.

It is to be understood that the zeolites used herein are not of thefibrous type, e.g., various Mordenites and some type Y zeolites, sincethese may cause asbestos-type safety issues. Accordingly, the term"zeolite" as used herein is intended to encompass only the nonfibrouszeolites. Moreover, it is preferred that the zeolites used herein besubstantially hydrophobic, since they generally must function to adsorbodors in the presence of body fluids when used in the articles andprocesses disclosed herein. While some naturally-occurring zeolites meetthe objectives of this invention, the synthetic zeolites of the typesavailable in commerce are generally more preferred.

In general terms, traditional zeolites comprise an aluminate/silicateframework, with associated cations, M, providing overall electricalneutrality. Empirically, the zeolite framework can be represented as

    x AlO.sub.2 . y SiO.sub.2

and the electrical neutral zeolite as

x/n M . x AlO₂. y SiO₂. zH₂ O

wherein: x and y are each integers, M is a cation and n is the charge onthe cation. As noted by the empirical formula, zeolites may alsocomprise waters of hydration (z H₂ O). Reference to the literature willillustrate that M can be a wide variety of cations, e g., H⁺ (i.e.protonic) Na⁺, K⁺, NH₃₊, alkylammonium, and the like. The practice ofthe present invention does not require any particular selection ofcation; accordingly, hydrogen ion and sodium ion are convenient andpreferred.

It is to be understood that a first class of preferred zeolites usedherein has entirely different ratios of SiO₂ /AlO₂ than the zeolitesdisclosed in U.S. Pat. Nos. 4,795,482 and 4,826,497. Stated otherwise,the ratio of integers x and y in this first class of zeolites is suchthat the zeolites are typically characterized as "intermediate"silicate/aluminate zeolites, whereas those of U.S. Pat. Nos. 4,795,482and 4,826,497 are "high" silicate/aluminate zeolites.

While not intending to be limited by theory, it appears that thesilicate/aluminate ratios of the "intermediate" zeolites used in thepractice of this invention result in several advantages over the "high"zeolites. First, the intermediate zeolites have a higher capacity foramine-type odors than the high zeolites. This is important tocontrolling urine and menses odors. Second, the intermediate zeoliteshave a larger surface area (700-800 m^(2/) g) than the high zeolites(ca. 400 m² /g). This results in more efficient odor adsorptivity, on awt./wt. basis; or, in the alternative, allows less zeolite to be used toadsorb a given amount of odor. Third, the intermediate zeolites appearto be somewhat more tolerant to moisture, and retain more of theirodor-adsorbing capacity in the presence of water. The "intermediate"zeolites used in this invention are characterized by SiO₂ /AlO₂ molarratios of less than about 10. Typically, the molar ratio of SiO₂ /AlO₂will range from about 2 to about 10.

The synthesis of intermediate zeolites forms no part of the presentinvention since various syntheses are known in the extensive zeoliteliterature. The following is given simply by way of illustration, andnot limitation, of a synthetic procedure.

Zeolite Synthesis

In general, zeolites are synthesized by hydrothermal crystallization ofalkaline (pH>8 and preferably higher) reactant mixtures. The synthesiscan be viewed as 3 major stages with each having sub-steps: (1)combining and gelation of reactants; (2) crystallization; and (3)post-treatment. The resulting zeolite is not only a function of thereactant mixture but also is equally a function of the syntheticconditions. External factors such as temperature, pressure, time, etc.highly influence the crystalline structure. Ion exchange can yield H⁺,Na⁺, K⁺, etc. forms. For traditional zeolites, the reactants commonlyconsist of:

    silica source+ alumina source+ base+ water

A host of starting reactants are available; some typical silica andalumina sources are noted as follows. Silica sources include: silicates;silica sol; silicic acid; silica gels; silica glass; minerals; and otherzeolites. Alumina sources include: aluminum hydroxide; aluminum salts;metal aluminates; aluminum nitrate; aluminum sulfate; pseudoboehmite;and various minerals.

While different starting materials can yield zeolites, the same zeolitecan be made from different reactants. Some reactant variablesinfluencing the structure and composition of the final zeolite are:

the identity, ratio and order of addition of the reactants;

the strength of the base;

the temperature (ambient to ca. 100° C.);

mechanical agitation such as stirring; and

the gelation time (1 hour to days).

Once the desired gelation is achieved, the gel is transferred to ateflon or stainless steel container and placed in an autoclave. Crystalformation begins as the gel is subjected to constant or variabletemperature at autogeneous pressure for an indefinite time. There arebasically 3 recognized phases during transformation of the gel tocrystals. The phases are (1) induction or nucleation (first crystalappears); (2) crystal growth; and (3) phase transformation. Some factorsinfluencing the rate at which crystals form and grow are thetemperature, pH, addition of seed crystals or templating materials forstructure directing, stirring and centrifugation.

After phase transformation, the slurry is removed from the autoclave andfiltered. The crystals are washed and dried at ca. 100° C. Furthermodifications are possible if so desired.

Post-Synthesis Modifications

Some post-synthesis modifications are a means of obtaining othertraditional zeolites. For instance, counter ions can be exchanged suchas:

    Na-zeolite+NH.sub.4 Cl→NH.sub.4 --zeolite

or

    Na-zeolite+HCl→H-zeolite

imparting unique adsorptive forces and modifying the pore size of, forexample, an A, X or Y zeolite. Additionally, stabilization oftraditional zeolites is possible. For example, a typical method ofsynthesizing an ultrastable zeolite Y (USY) such as "VALFOR CP300-56" isas follows:

    NaY+NH.sub.4 +or NH.sup.+ exchange→NH.sub.4 NaY+calcine (650°-800° C.)→USY

Synthesis of Special Zeolites

Several post-synthesis modification methods exist for making specialzeolites. The methods include (1) pore modification; (2) surfacemodification; and (3) structural change. The first two methods consistof adsorbing species by chemical vapor deposition inside or on thezeolite. Pore modifiers such as SiH₄ and BH₃ and surface modifiers suchas Si(OCH₄)₄, SiCl₄, TiCl₄ and SeCl₄ have been used to impart new uniqueproperties to the zeolite. The most frequently used structural changemethod is to remove alumina from the main framework (i.e.,de-aluminate). De-alumination can be performed by one of several routessuch as (1) acid leaching; (2) steam (700°-900° C.); or (3) treatmentwith SiCl₄ at cold temperatures. An example of de-alumination is:

    Zeolite Y+H.sub.4 EDTA→de-aluminated Zeolite Y

The following references further illustrate the synthesis ofintermediate zeolites of the type employed herein: Lok, B. M., Cannan,T. R., and Messina, C. A., "The Role of Organic Molecules in MolecularSieve Synthesis" Zeolites 3, 282-291 (1983); Barrer, R. M. "Zeolites andTheir Synthesis" Zeolites 1, 130-140 (1981); ZEOLITES FOR THE NINETIES,Proceedings of the 8th International Zeolite Conference, Eds. P. A.Jacobs and R. A. van Santen (1989) pages 119-372; and MOLECULAR SIEVES,Adv. Chem. Ser. 121, Eds. W. M. Meier and J. B. Uytterhoeven (1973).

A wide variety of intermediate zeolites suitable for use herein arecommercially available from commercial suppliers such as PhiladelphiaQuartz and Conteka. Such materials are sold under various commercial andtrade names such as VALFOR CP301-68, VALFOR 300-63, VALFOR CP300-35 andVALFOR CP300-56, from Philadelphia Quartz, and the CBV100 series (otherthan Mordenite, as noted above) of zeolites from Conteka, preferably inNa⁺ or H⁺ forms.

A second type of odor-controlling agent which can be optionally employedin the practice of this invention in combination with the aforesaidintermediate ratio zeolites comprises the "high ratio" zeolites. Suchmaterials include, for example, the well-known "molecular sieve"zeolites of the ZSM, beta zeolite, etc., type (generally in the 1-10micron particle size range) and the zeolite materials marketed under thetrade name ABSCENTS by the Union Carbide Corporation and UOP, and whichare typically available as a white powder in the 3-5 micron particlesize range (see: ABSCENTS, A New Approach for Odor Control by A. J.Gioffre, copyright 1988 by the Union Carbide Corporation). Suchmaterials are preferred over the 37 intermediate" zeolites when controlof odors associated with sulfur compounds, e.g., thiols, mercaptans, aswell as some control of amine odors, is desired.

The use of zeolites of the ABSCENTS type to control odors is fullydescribed in U.S. Pat. 4,795,482, Jan. 3, 1989, to Gioffre and Marcus.In general, these molecular sieve odor-controlling agents appear tofunction by entrapping by chemical adsorption odoriferous substanceswithin their molecular lattice structures. Whatever their mode ofaction, these odor-controlling agents can be characterized by theirphysical parameters, as follows. These agents are reported by Gioffreand Marcus to be crystalline siliceous molecular sieves in which atleast about 90, and preferably at least about 95, percent of theframework tetrahedral oxide units are SiO₂ tetrahedra and which have asorptive capacity for water at 25° C. and 4.6 of less than 10 weightpercent. In the case of aluminosilicate molecular sieves, those "highratio" zeolite odor-controlling agents have a framework SiO₂ /AlO₂ molarratio of from about 35 to infinity, and preferably from 200 to 500. Suchsiliceous molecular sieves have a pore diameter of at least 5.5Angstroms, preferably at least 6.2 Angstroms. Preferably the adsorptioncapacity for water vapor at 25° C. and a water vapor pressure (P/Po) of4.6 is less than 6 weight percent. As stated by Gioffre and Marcus, theefficacy of these molecular sieves is not dependent on the presence ofthe water of hydration in the internal cavities of the microporousstructure as a result of their hydrothermal formation. In fact, at leasta major proportion, usually substantially all, of this original water ofhydration is removed in the process of removing any pore-blockingtemplating agent which may be present in the adsorbent. Calcinationeffectively removes any organic moieties. Also, water washing, leachingor washing with a caustic or dilute mineral acid solution isadvantageously utilized to remove extraneous synthesis reactants fromthe pore system. Lowering of the alkali metal content, particularly thenonzeolitic, i.e., occluded alkali metal compounds can also bebeneficial. These procedures also serve to remove the original water ofhydration.

As further disclosed by Gioffre and Marcus, such siliceous molecularsieves include the microporous crystalline aluminosilicates, i.e., thezeolitic molecular sieves as well as the so-called silica polymorphs.With respect to the latter compositions, their crystal lattices areideally formed entirely of SiO₂ tetrahedral units, but theas-synthesized forms commonly contain at least trace amounts of aluminumderived from aluminum impurities in the synthesis reagents. Thealuminosilicate molecular sieves comprise the large class of well-knowncrystalline zeolites. These high-silica molecular sieves are eithercommercially available or are prepared by methods well-known in the art,involving direct hydrothermal synthesis or involving certain types ofcrystal lattice dealuminations. A comprehensive review article by E. M.Flanigen concerning both "high" Si/Al zeolites and silica molecularsieves is published in "Proc. 5th Int. Conf. Zeolites, Naples, 1980", L.V. C. Rees, ed., Heyden, London, pp. 760-780. It is to be understoodthat all such materials are referred to herein simply as "zeolites", forconvenience.

With respect to the foregoing ABSCENTS odor-controlling agents, it isimportant that their pore system be open so that the internal cavitiesof the crystals be accessible to the odor molecules. In the case of thealuminosilicates or silica polymorphs produced using large organictemplating ions such as tetraalkylammonium ions, it is necessary toremove charge balancing organic ions and any occluded templatingmaterial in order to permit adsorption of the odor molecules. In such aremoval process and also in the removal of inorganic debris, theoriginal water of hydration is also removed. Upon exposure to theatmosphere, a portion of the water of hydration is reacquired, but thisdoes not affect the characteristics of the molecular sieves which arepreferred for the practice of the present invention, i.e., the molecularsieves can be employed in either a hydrated or dehydrated state, but, ingeneral, the dehydrated state is preferred. In the case of most of thedealumination procedures referred to above, the original water ofdehydration is also removed, and can similarly be replaced, if desired,for the practice of the invention.

More specifically, Gioffre and Marcus disclose that the class of theirdisclosed medium to large pore siliceous molecular sieves, from whichthe original, as-synthesized water of hydration has been substantiallyremoved, and which have a capacity for adsorbed water of not greaterthan 10, and preferably not greater than 6, weight percent when measuredat 25° C. and a water vapor pressure (P/Po) of 4.6, function in anextraordinary manner with respect to odor el imination. Many of thesynthetic zeolites prepared using organic templating agents are readilyprepared in a highly siliceous form--some even from reaction mixtureswhich have no intentionally added aluminum. These zeolites are markedlyorganophilic and include ZSM-5 (U.S. Pat. No. 3,702,886); ZSM-11 (U.S.Pat. No. 3,709,979); ZSM-35 (U.S. Pat. No. 4,016,245); ZSM-23 (U.S. Pat.No. 4,076,842); and ZSM-38 (U.S. Pat. No. 4,046,859) to name only a few.According to these authors, the silica molecular sieves known assilicalite and F-silicalite are particularly suitable for use asodor-controlling agents. These materials are disclosed in U.S. Pat. Nos.4,061,724 and 4,073,865, respectively. To the extent the aforesaidsiliceous sieves are synthesized to have SiO₂ /AlO₂ ratios greater than35, they are frequently suitable for use in the present articles withoutany additional treatment to increase their degree of hydrophobicity.Molecular sieves which cannot be directly synthesized to have both thedesired high Si/Al and/or degree of hydrophobicity ratios can besubjected to dealumination techniques, fluorine treatments and the like,which result in organophilic zeolite products. High-temperature steamingprocedures for treating zeolite Y which result in hydrophobic productforms are reported by P. K. Maher et al, "Molecular Sieve Zeolites",Advan. Chem. Ser. 101, American Chemical Society, Washington, D.C.,1971, p. 266. A more recently reported procedure applicable to themanufacture of "high" zeolite species generally, involves dealuminationand the substitution of silicon into the dealuminated lattice site. Thisprocess is disclosed in U.S. Pat. No. 4,503,023 issued Mar. 5, 1985 toSkeels et al. Halogen or halide compound treatments for zeolites toincrease their hydrophobicity are disclosed in U.S. Pat. Nos. 4,569,833and 4,297,335. Steam-treated zeolite Y, prepared per U.S. Pat. No.4,331,694, and denominated "LZ-10", is a particularly usefulodor-control 1 ing agent.

Various other modified zeolite-type materials, such as themanganese-aluminum-phosphorus-silicon-oxide molecular sieves describedin U.S. Pat. No. 4,793,833, Lok et al, assigned to UOP, can be usedherein. See also U.S. Pat. Nos. 4,604,110; 4,437,429; and 4,648,977, forother zeolitic odor-controlling compositions.

II. Absorbent Gelling Material-- As is well-known from recent commercialpractice, absorbent gelling materials (sometimes referred to as"super-sorbers") are becoming broadly used in absorbent articles. Ingeneral, such AGM's have been used only for their fluid-absorbingproperties. Such materials form hydrogels on contact with water (e.g.,with urine, blood, and the like). One highly preferred type ofhydrogel-forming, absorbent gelling material is based on polyacids,especially polyacrylic acid. Hydrogel-forming polymeric materials ofthis type are those which, upon contact with fluids (i.e., liquids) suchas water or body fluids, imbibe such fluids and thereby form hydrogels.In this manner, fluid discharged into the absorbent structures hereincan be acquired and held. These preferred absorbent gelling materialswill generally comprise substantially water-insoluble, slightlycross-linked, partially neutralized, hydrogel-forming polymer materialsprepared from polymerizable, unsaturated, acid-containing monomers. Insuch materials, the polymeric component formed from unsaturated,acid-containing monomers may comprise the entire gelling agent or may begrafted onto other types of polymer moieties such as starch orcellulose. Acrylic acid grafted starch materials are of this lattertype. Thus the preferred absorbent gelling materials include hydrolyzedacrylonitrile grafted starch, acrylic acid grafted starch,polyacrylates, maleic anhydride-based copolymers and combinationsthereof. Especially preferred absorbent gelling materials are thepolyacrylates and acrylic acid grafted starch.

Whatever the nature of the polymer components of the preferred absorbentgelling materials, such materials will in general be slightlycross-linked. Crossl inking serves to render these preferredhydrogel-forming absorbent materials substantially water-insoluble, andcross-linking also in part determines the gel volume and extractablepolymer characteristics of the hydrogels formed therefrom. Suitablecross-linking agents are well known in the art and include, for example,(1) compounds having at least two polymerizable double bonds; (2)compounds having at least one polymerizable double bond and at least onefunctional group reactive with the acid-containing monomer material; (3)compounds having at least two functional groups reactive with theacid-containing monomer material; and (4) polyvalent metal compoundswhich can form ionic cross-1 inkages. Cross-linking agents of theforegoing types are described in greater detail in Masuda et al; U.S.Pat. No. 4,076,663; Issued Feb. 28, 1978. Preferred crosslinking agentsare the di- or polyesters of unsaturated mono-or polycarboxylic acidswith polyols, the bisacrylamides and the di-or triallyl amines.Especially preferred cross-linking agents areN,N'-methylenebisacrylamide, trimethylol propane triacrylate andtriallyl amine. The cross-linking agent will generally comprise fromabout 0,001 mole percent to 5 mole percent of the preferred materials.More preferably, the cross-linking agent will comprise from about 0.01mole percent to 3 mole percent of the absorbent gelling materials usedherein.

The preferred, slightly cross-linked, hydrogel-forming absorbent gellingmaterials will generally be employed in their partially neutralizedform. For purposes described herein, such materials are consideredpartially .neutralized when at least 25 mole percent, and preferably atleast 50 mole percent of monomers used to form the polymer are acidgroup-containing monomers which have been neutralized With asalt-forming cation. Suitable salt-forming cations include alkali metal,ammonium, substituted ammonium and amines. This percentage of the totalmonomers utilized which are neutralized acid group-containing monomersis referred to as the "degree of neutralization." Typically, commercialabsorbent gelling materials have a degree of neutralization somewhatless than 90%.

The preferred absorbent gelling materials used herein are those whichhave a relatively high capacity for imbibing fluids encountered in theabsorbent articles; this capacity can be quantified by referencing the"gel volume" of said absorbent gelling materials. Gel volume can bedefined in terms of the amount of synthetic urine absorbed by any givenabsorbent gelling agent buffer and is specified as grams of syntheticurine per gram of gelling agent.

Gel volume in synthetic urine (see Brandt, et al, below) can bedetermined by forming a suspension of about 0.1-0.2 parts of driedabsorbent gelling material to be tested with about 20 parts of syntheticurine. This suspension is maintained at ambient temperature under gentlestirring for about 1 hour so that swelling equilibrium is attained. Thegel volume (grams of synthetic urine per gram of absorbent gellingmaterial) is then calculated from the weight fraction of the gellingagent in the suspension and the ratio of the liquid volume excluded fromthe formed hydrogel to the total volume of the suspension. The preferredabsorbent gelling materials useful in this invention will have a gelvolume of from about 20 to 70 grams, more preferably from about 30 to 60grams, of synthetic urine per gram of absorbent gelling material.

Another feature of the most highly preferred absorbent gelling materialsrelates to the level of extractable polymer material present in saidmaterials. Extractable polymer levels can be determined by contacting asample of preferred absorbent gelling material with a synthetic urinesolution for the substantial period of time (e.g., at least 16 hours)which is needed to reach extraction equilibrium, by then filtering theformed hydrogel from the supernatant liquid, and finally by thendetermining the polymer content of the filtrate. The particularprocedure used to determine extractable polymer content of the preferredabsorbent gelling agent buffers herein is set forth in Brandt, Goldmanand Inglin; U.S. Pat. No. 4,654,039; Issued Mar. 31, 1987, Reissue32,649. The absorbent gelling materials which are especially useful inthe absorbent articles herein are those which have an equilibriumextractables content in synthetic urine of no more than about 17%,preferably no more than about 10% by weight of the absorbent gellingmaterial.

The absorbent gelling materials hereinbefore described are typicallyused in the form of discrete particles. Such absorbent gelling materialscan be of any desired shape, e.g., spherical or semi-spherical, cubic,rod-like polyhedral, etc. Shapes having a large greatestdimension/smallest dimension ratio, like needles and flakes, are alsocontemplated for use herein. Agglomerates of absorbent gelling materialparticles may also be used.

The size of the absorbent gelling material particles may vary over awide range. For reasons of industrial hygiene, average particle sizessmaller than about 30 microns are less desirable. Particles having asmallest dimension larger than about 2 mm may also cause a feeling ofgrittiness in the absorbent article, which is undesirable from aconsumer aesthetics standpoint. Furthermore, rate of fluid absorptioncan be affected by particle size. Larger particles have very muchreduced rates of absorption. Preferred for use herein are absorbentgelling material particles substantially all of which have a particlesize of from about 30 microns to about 2 mm. "Particle Size" as usedherein means the weighted average of the smallest dimension of theindividual particles.

The amount of absorbent gelling material particles used in absorbentcores will depend upon the degree of absorbent capacity desired, andwill generally comprise from about 2% to 50% by weight of the absorbentcore, more typically from about 5% to 20% by weight of the absorbentcore.

When absorbent gelling material particles are to be used in the cores ofthe absorbent articles herein, such cores can be prepared by any processor technique which provides a web comprising a combination of the fibersand the gelling material particles. For example, web cores can be formedby air-laying a substantially dry mixture of hydrophilic fibers andabsorbent gelling material particles and, if desired or necessary, bydensifying the resulting web. Such a procedure is described more fullyin Weisman and Goldman; U.S. Pat. No. 4,610,678; Issued Sep. 9, 1986. Asindicated in this U.S. Pat. No. 4,610,678, the air-laid webs formed bysuch a procedure will preferably comprise substantially unbonded fibersand will preferably have a moisture content of 10% or less.

The density of the absorbent cores which comprise webs of hydrophilicfibers and absorbent gelling material particles can be of importance indetermining the absorbent properties of the cores and of the absorbentarticles in which such cores are employed. The density of such absorbentcores herein will preferably be in the range of from about 0.06 to about0.3 g/cm³, and more preferably within the range of from about 0.09 toabout 0.22 g/cm³. Typically the basis weight of the absorbent coresherein can range from about 0.02 to 0.12 g/cm².

Density values for cores of this type can be calculated from basisweight and caliper. Caliper is measured under a confining pressure of0.137 psi (0.94 kPa). Density and basis weight values include the weightof the absorbent gelling materials and the odor-control material.Density of the cores herein need not be uniform throughout the core.Within the density ranges hereinbefore set forth, the cores can containregions or zones of relatively higher or relatively lower density.

III. Additional Absorbents-- Typically, finished absorbent articles willcontain additional fibrous absorbent material such as cotton fluff,cellulose pulp, chemithermomechanical pulp, and the like, well-known incommercial practice.

IV. Front-Face Material

The finished articles herein will typically be provided with afluid-receiving facing material. The front-face (or, "topsheet")material used herein is preferably a "nonstaining" hydrophobic,fluid-permeable sheet. Hydrophobic sheet materials of the type typicallyemployed in the practice of this invention can be prepared by methodswell-described in the patent literature. For example, according to theprocess of U.S. Pat. No. 4,324,246, Mullane and Smith, Apr. 13, 1982, asample of thermoplastic material such as 0.0038 cm thick polyethylenefilm is heated above its softening point. (The softening point is thetemperature at which the thermoplastic material can be formed or moldedand is less than the melting point of the material.) The heatedthermoplastic material in sheet form is then brought into contact with aheated forming screen. The forming screen is preferably an aperturedwire mesh screen having the desired aperture size, pattern andconfiguration. A vacuum is used to draw the heated film against theforming screen, thereby forming the film into the desired pattern andhaving the desired hole sizes. While the vacuum is still being appliedto the film, a jet of hot air is passed over the film. The hot air jetperforates the film in a pattern corresponding to the pattern and sizeof apertures in the forming screen.

Fluid-permeable sheets prepared in the manner of the Mullane et alpatent are conveniently referred to as "formed films". The caliper ofsuch films is important since, if the caliper is too great, liquid mayaccumulate in the apertures and not readily pass therethrough. For themanufacture of absorbent articles such as diapers, catamenials,incontinence articles, and the like, the sheets typically have a caliperof less than about 0.075 cm, or preferably less than about 0.064 cm.

Another formed-film sheet material useful herein is the resilient,3-dimensional web exhibiting a fiber-like appearance and tactileimpression, comprising a fluid-impervious plastic material, with saidweb having a multiplicity of apertures, the apertures being defined by amultiplicity of intersecting fiberlike elements, all as disclosed inU.S. Pat. No. 4,342,314, Radel and Thompson, Aug. 3, 1982. The Radel andThompson sheet materials can be prepared using hydrophobic plastics suchas polyethylene, polypropylene, PVC, and the like, and are well-knownfor use in absorbent products such as catamenials, and the like.

Yet another type of sheet material useful herein is described in U.S.Pat. No. 3,929,135, Thompson, Dec. 30, 1975, and consists of hydrophobicpolymer films having holes which are in the form of tapered capillaries.These "tapered capillary" sheets are also known for use in absorbentarticles, including adult incontinence articles. They may be preparedfrom various hydrophobic polymers, as mentioned hereinabove; typically,low density polyethylene having thickness of from 0.0025 to 0.0051 cm isemployed.

Reference to U.S. Pat. No. 3,929,135 can be made in order to furthervisualize tapered capillary sheets. In use, the apices of thecapillaries in such tapered capillary topsheets are in contact with theunderlying absorbent core material. Generally, tapered capillaries arein the form of a frustrum of a conical surface, but it is to beunderstood that any generally tapered structure, such as a frustrum of apyramid or the like with a triangular, square, or polygonal base, iswithin the term "tapered capillary"; circular tapered capillaries,however, are used in this description for convenience. It is also to beunderstood that the tapered capillaries can be asymmetric (i.e., theangle of taper on one side can be different from that on another side)and that the angle of taper can change continuously (i.e., be curved)over the distance from base to apex. In the latter case, the angle oftaper is defined as the angle of the tangent to the side of thecapillary at its point of minimum apex opening dimension. The angle oftaper suitable for use in topsheets according to the practice of thisinvention is from about 10° to about 60°.

Base opening dimension of the capillaries is defined as the maximum openmeasurement in the plane of topsheet at said tapered capillary. Apexopening dimension is defined as the maximum open measurement in the apexof said tapered capillary, which apex is remote from the plane of thetopsheet. When the tapered capillary is in the form of a frustrum of aconical surface, the base and apex opening dimensions are, respectively,the base diameter and the apex diameter. Base diameter and apex diameterare hereinafter used interchangeably with, respectively, base openingdimension and apex opening dimension.

The tapered capillary apex diameter is a diameter which will allowliquid to readily pass from the surface of the topsheet to theunderlying absorbent core. The apex diameter is from about 0.004 toabout 0.100 inch (0.010 to 0.254 centimeter), preferably from about0.005 to about 0.020 inch (0.013 to 0.051 centimeter).

The tapered capillary base diameter is selected to satisfy two criteria.The first of these is the subjective feel of the surface of the topsheetwhich contacts the skin of the user. It has been discovered thatpolyethylene can be made to exhibit pleasing, clothlike, non-waxyattributes when the base diameter is within the range from about 0.006to about 0.250 inch (0.015 to 0.635 centimeter). Preferably, the basediameter should be within the range of from about 0.030 to about 0.060inch (0.076 to 0.152 centimeter). The second criterion is that thecapillary base diameter be small enough to allow an expected liquiddroplet to bridge across at least one capillary. This criterion issatisfied by the above dimensions for disposable diapers and sanitaryitems.

The height of the tapered capillary is defined as the distance betweenthe outermost surface of the topsheet (i.e., that surface which normallycontacts the skin of the user) and the apex of the tapered capillary.This height, of course, depends upon apex diameter, base diameter, andangle of taper which have been selected as hereinbefore described. Theheight of the tapered capillary should provide a structure with aminimum tendency to collapse in use. The characteristics of the materialof construction of the topsheet in large measure determine suitableranges for the height. When the topsheet is low density polyethylene offrom 0.001 to 0.002 inch (0.003 to 0.005 cm) thickness and apex diameterand base diameter are in the preferred range, and angle of taper α is inits critical range, the height of the tapered capillary can be fromabout 0.003 to about 0,159 inch (0.008 to 0.404 centimeter).

A state of relative dryness on the surface of the topsheet implies thatmost of the liquid which contacts the topsheet is transferred through itto the absorbent element. This in turn implies that each isolateddroplet of fluid in contact with the topsheet must be in contact withthe base diameter of a tapered capillary. This state of affairs can bestbe achieved if the land area (the area of the topsheet that existsbetween the bases of the tapered capillaries) is maintained at aminimum. The minimum limiting value is the case where conical taperedcapillaries or pyramidal tapered capillaries are provided in closepacked array (where the periphery of the base of each capillary is incontact on all sides with the periphery of the base of adjacentcapillaries). The preferred arrangement of minimum land area tends toinsure that an individual droplet will contact at least one taperedcapillary. A preferred arrangement in disposable diapers is where thetapered capillaries as hereinbefore described are in ordered arrangementwith from about 30 to about 1500 tapered capillaries per square inch oftopsheet (5 to 231 per square centimeter).

Tapered capillary sheets can be manufactured in any of several ways wellknown in the art. One particularly suitable method is to provide aheated mold with male elements of the shape and arrangement of thedesired tapered capillaries (hereinafter a pin mold). Each male elementis secured in such a fashion that its apex extends away from the base ofthe pin mold. A portion of sheet material is brought into contact withthe heated pin mold between the mold and a resilient backing plate.Pressure is applied to the combination of mold, sheet and resilient backplate and tapered capillaries are formed in the sheet to make thetapered capillary topsheet. An alternate way of constructing thetopsheet is to subject a portion of liquid-impervious material to vacuumforming over an appropriate mold. After forming tapered capillary sheetsin one of the aforementioned ways, it may be necessary to physicallyremove material from the apices of the capillaries so as to insure thatthe apex diameters are the desired value. Such removal of material canbe accomplished by, for example, subjecting the apices to controlledabrasion or by heating the formed topsheet so as to melt open theapices. See, also, U.S. Pat. No. 4,629,643, Curro and Linman, Dec. 16,1986, for a microapertured polymeric film with improved tactileimpression, which can also be used in the practice of this invention.

A highly-preferred fluid-permeable formed-film sheet material which canbe employed in the practice of this invention is disclosed in U.S. Pat.4,463,045, Ahr et al, Jul. 31, 1984, and reference can be made to thatpatent to further assist visualization of the Ahr et al structures.

In general terms, the sheets provided by U.S. Pat. 4,463,045 aredesigned not only to provide a desirable cloth-like tactile impression,but also to substantially eliminate surface gloss. Thus, sheets made ofplastic do not have an undesirably shiny, "plasticky" appearance.

Such highly-preferred sheet materials can be succinctly described asbeing a macroscopically expanded three-dimensional plastic "web" havingat least one visible surface which appears substantially nonglossy whenexposed to light, substantially all of said visible surface exhibiting aregularly spaced, microscopic pattern of discrete surface aberrations,each of said surface aberrations having its amplitude orientedperpendicular to the surface in which said surface aberrationoriginates, each of said surface aberrations having a maximum dimensionof less than about 6 mils, as measured in a plane oriented substantiallyperpendicular to its amplitude, whereby said surface aberrations are notdiscernible to the normal naked eye when the perpendicular distancebetween the viewer's eye and the plane of said web is at least about 12inches, each of said surface aberrations also being free of planar areaswhich are large enough to inscribe a 4 mil diameter circle and so spacedrelative to all adjacent surface aberrations that the maximum diameterof any circle which can be inscribed on any planar surface intermediatesaid surface aberration and said adjacent surface aberrations on anyportion of said visible surface is less than about 4 mils, whereby anylight incident upon any portion of said visible surface is diffuselyreflected into a multiplicity of directions by said surface aberrationsso that said visible surface appears substantially nonglossy. The '045sheet materials can have at least a portion of said surface aberrationscomprising protuberances projecting generally outwardly from thesurface, and can have at least a portion of said surface aberrationscomprising depressions projecting generally inwardly from the surface ofsaid web.

The manufacture of these preferred sheets can be achieved by use of aforming screen or structure, as generally noted hereinabove, whichprovides said surface aberrations by virtue of "knuckles" on the supportmember. (The preparation of such sheets is described in great detail inU.S. Pat. No. 4,463,045, and their method of preparation forms no partof this invention.) In general, the resulting surface aberrationscorrespond to the knuckles of a woven mesh support structure whichdirectly contacts the visible surface of said plastic sheet duringproduction thereof.

In a preferred manufacturing method, the woven mesh support structurewhich directly contacts the visible surface of said sheet is comprisedof filaments having a diameter between about one and about two mils anda mesh count between about 160 filaments per lineal inch (2.54 cms) by160 filaments per lineal inch (2.54 cms) and about 400 filaments perlineal inch (2.54 cms) by 400 filaments per lineal inch (2.54 cms).

Preferred sheets herein are those wherein said surface aberrations havean average amplitude of at least about 0.2 mils, more preferably atleast about 0.3 mils. Most preferably, sheets having an amplitude ofeach of said surface aberrations, as measured perpendicular to thesurface in which said surface aberration originates, within the range ofabout ±20%, desirably ±10%, of the average value of the amplitude forall adjacent surface aberrations are used.

"One-way" sheets whose back faces are treated with hydrophilic latex aredescribed in U.S. Pat. No. 4,735,843, Noda, Apr. 5, 1988, and these canalso be employed herein.

In addition to the sophisticated apertured materials mentionedhereinabove, the practice of the present invention may also beundertaken with hydrophobic sheet materials having simple holes punchedtherethrough. It will be understood from the foregoing that theaforesaid, preferred, "sheet" or "film" materials used in the practiceof this invention are substantially different from fibrous nonwovenmaterials, which are characterized by a large number of fibers whichoverlap each other throughout the thickness of the material. Moreover,such sheet materials are made from materials (preferably, hydrophobicthermoplastic polymeric materials) which provide a clean-appearing,stain-resistant or "non-staining" surface, in USe.

Other topsheet materials which can be used herein include, for example,various nonabsorbent fibrous or filamentous network sheets which areaqueous-fluid-permeable by virtue of a multiplicity of holes or channelspassing therethrough. Such sheet materials can be prepared by methodswell-described in the patent literature. For example, according to theprocess of U.S. Pat. No. 4,636,419, Madsen et al, Jan. 13, 1987, sheetscomprising a network of ribboned filaments of two dissimilar chemicaltypes, and with two dissimilar melting or softening points, arecontacted and cooled to allow the formation of a network sheetcharacterized by said different transverse and longitudinal polymermaterials. Such sheets can be used in the practice of this invention.

Another sheet material useful herein is the formaminous net comprising areticular network of polymeric filaments, said net comprising two arraysof filaments oriented at a displacement angle of 20-90 degrees.Reference can be made to European Patent Application 0215417, filed Jun.9, 1986, Sneyd et al, to further assist visualization of this sheet. Theaforesaid sheet materials can be prepared using hydrophobic plasticssuch as polyethylene, polypropylene, PVC, and the like, and arewell-known for use in absorbent products such as catamenials, and thelike. Such sheet materials typically have a basis weight of 0.5-5.0ounces/yd² (0.0016 g/cm² --0.016 g/cm²), a caliper of 5-25 mils, an openarea of 30-80% and a mesh of 20-40. Conventional nonwoven topsheets canalso be employed.

V. Backing Sheet

The backing sheet is conventional, and can comprise a fluid-imperviouspolymer sheet, for example polyethylene or polypropylene, that is thinenough to be flexible. A polyethylene sheet 0.001-0.5 mm thick istypical. Flushable or biodegradable backing sheets can also be used,e.g., with pantiliner devices herein.

VI. Optional Retaining Means

The absorbent structures herein can optionally, but preferably, beprovided with means to hold them in place on or near the user's body toallow the structures to perform their intended function. For example,diapers and incontinence garments can be provided with well-knowncommercially-available tape fasteners. Sanitary napkins can be providedwith glue stripes facing outward on their backsheet in well-knownfashion. Various pins, clips and fasteners of wellknown types canoptionally be employed.

VII. Optional Adjunct Odor-Controlling Materials13

The compositions and articles of this invention can also contain aneffective, i.e., odor-controlling, amount of various additionalnon-zeolite odor-controlling materials to further expand their capacityfor controlling odors, as well as the range of odor types beingcontrolled. Such materials include, for example, activated carbon,kieselguhr, cetyl pyridinium chloride, and the like. However,antimicrobial metal ions do not form part of the zeolites herein. Suchmaterials typically comprise 0.01% to 15% of the compositions herein.Stated otherwise, materials such as activated carbon can typically bepresent at the 0.1 g to 5.0 g level in absorbent articles of the typedisclosed herein to provide additional odor control benefits.

EXAMPLE I

Pads suitable for use as an absorbent structure in diapers, sanitarynapkins, and the like comprise a substantially homogeneous blend of thefollowing.

    ______________________________________                                        Ingredient          Percent (wt)                                              ______________________________________                                        Kraft Cellulose Fibers (SSK*)                                                                     72                                                        Intermediate Zeolite**                                                                            14                                                        ______________________________________                                         *Southern Softwood Kraft.                                                     **Available as VALFOR CP30056.                                           

EXAMPLE II

A lightweight pantiliner suitable for use between menstrual periods, andwhich can be disposed of in a toilet (i.e., "flushable") comprises a pad(surface area 117 cm² ; SSK air felt 3.0 g) containing 1.5 g of theintermediate zeolite particles (as VALLFOR CP301-68), said pad beinginterposed between the topsheet of U.S. Pat. No. 4,463,045 and afibrous, nonwoven, flushable backsheet.

EXAMPLE III

A mixed odor-controlling agent. is as follows.

    ______________________________________                                        Ingredient           Percent (wt)                                             ______________________________________                                        ABSCENTS (avg. 5 microns)                                                                          50                                                       VALFOR CP300-35 (10 microns)                                                                       50                                                       ______________________________________                                    

EXAMPLE IV

A catamenial product in the form of a sanitary napkin having two flapsextending outward from its absorbent core is prepared using the pad ofExample I (surface area 117 cm² ; 8.5 g SSK air felt; 2.0 g zeolite SiO₂AlO₂ 8.5), per the design of U.S. Pat. No. 4,687,478, Van Tillburg, Aug.18, 1987. The nonglossy sheet of U.S. Pat, 4,463,045, is used as thetopsheet.

EXAMPLE V

A disposable baby diaper using the odor-control pad of Example I isprepared as follows. The dimensions listed are for a diaper intended foruse with a child in the 6-10 kilogram size range. These dimensions canbe modified proportionately for different size children, or for adultincontinence briefs, according to standard practice.

1. Backsheet: 0.025-0.070 mm polyethylene; width at top and bottom 33cm; notched inwardly on both sides to a width-at-center of 28.5 cm;length 50.2 cm.

2. Topsheet: tapered capillary polyethylene topsheet, per U.S. Pat. No.3,929,135, described hereinabove; width at top and bottom 33 cm; notchedinwardly on both sides to a width-at-center of 28.5 cm; length 50.2 cm.

3. Absorbent core: air-laid wood pulp fibers per Example I; Taberstiffness range 7-9.5, 8.4 mm thick, calendered; width at top and bottom28.6 cm; notched inwardly at both sides to a width-at-center of 10.2 cm;length 44.5 cm; 3.2 g of zeolite powder SiO₂ AlO₂ 7.0; 5 micron particlesize dispersed in said core.

4. Elastic leg bands: four individual rubber strips (2 per side); width4.77 mm; length 370 mm; thickness 0.178 mm (all the foregoing dimensionsbeing n the relaxed state).

The diaper of Example V is prepared in standard fashion by positioningthe core-plus-odor control material covered with the topsheet on thebacksheet and gluing.

The elastic bands (designated "inner" and "outer", corresponding to thebands closest to, and farthest from, the core, respectively) arestretched to ca. 50.2 cm and positioned between the topsheet/backsheetalong each longitudinal side (2 bands per side) of the core. The innerbands along each side are positioned ca. 55 mm from the narrowest widthof the core (measured from the inner edge of the elastic band). Thisprovides a spacing element along each side of the diaper comprising theflexible topsheet/backsheet material between the inner elastic and thecurved edge of the core. The inner bands are glued down along theirlength in the stretched state. The outer bands are positioned ca. 13 mmfrom the inner bands, and are glued down along their length in thestretched state. Since the topsheet/backsheet assembly is flexible, theglued-down bands contract to elasticize the sides of the diaper.

It will be understood that the practice of the present invention appliesnot only to human odors, but also to animal odors.

EXAMPLE VI

A cat litter product comprises the following components.

    ______________________________________                                        Ingredient        Percent (wt.)                                               ______________________________________                                        Zeolite*          15                                                          Comminuted Cellulose**                                                                          82                                                          Activated Carbon  3                                                           ______________________________________                                         *As CBV100 series                                                             **Compacted in granular form.                                            

As can be seen from the foregoing, the compositions of this inventionare used in odor-controlling amounts to achieve the desired benefits.This amount can, of course, vary, depending on the intended end-use andseverity of the odor. Typically, catamenial products will employsufficient amounts of said composition to deliver from at least about0.2 g. to about 0.4 g. of the odor-controlling agent. To assist theformulator, a simple test of odor-controlling capacity of suchcompositions comprises placing the odor-controlling composition in anabsorbent pad of the desired type and uniformly adding a 5 ml. aliquotof a defined onion/ammonia odor medium (20 g. commercial onion powder,900 mls H₂ O containing 7.5 g. NaHPO₄.7H₂ O, 4.5 g. 1.8 g. MgCl₂.6H₂ O,3.0 g NaCl, 15.0 g. urea; 10.0 ml of 1 normal HCl; stirred 4 hours,filtered; NH₄ OH and H₂ O added to yield NH₄ OH concentration 500-1500ppm, as desired). After equilibrating for 1 hour in a closed containerwith a sniff port, the odor-controlling capacity of the composition canbe judged and the amounts used can be adjusted accordingly.

In the event the zeolites herein are optionally to be used inconjunction with activated carbon, it is preferred (for aestheticsreasons) to coat the carbon with the zeolite using a binder. Thefollowing illustrates this in detail.

VIII. Preparation of Carbon/Zeolite/Binder Particles

A simple, yet effective, method for preparing the particles hereinemploys a fluidized bed coating apparatus, as described more fullyhereinafter. However, it will be appreciated that other types of coatingapparatus, agglomerators, or the like, can also be used to prepare suchparticles. While various coating processes described in the technicalliterature can be adapted for use herein, the following is intended toassist the formulator in the selection of processing methods from avariety of available equipment.

Fluid Bed Coating

There are a number of variations on fluid bed coating.

a. Agglomerating fluid bed: These beds are used for agglomeration and inthe present process would not do a good job of masking the color of thecharcoal. In a typical agglomeration process, a binding fluid is pumpedinto the fluid bed so that small particles stick together and formlarger particles. If zeolite and charcoal are mixed in the bed and thensprayed in a binding solution, the resulting large particles wouldcomprise many smaller particles of zeolite and charcoal. This is arandom process and masking would not be good. Further difficulties arisein this system when trying to "glue" particles of very different sizesand physical properties.

b. Top spray fluid bed: The coating solution is sprayed downward ontothe top of a fluidized bed where the air is moving up through the bed.It is sometimes possible to form a good coating on a single particleusing this technique, but it can be difficult to control because of thetop churning surface of the bed. The best individual particles coatedare very large (greater than 1 m).

c. Bottom spray fluid bed (Wurster): This is the most effective way toget a good coating onto an individual particle, because of the orderedflow up the center draft tube and because the flow of the spray andparticle are in the same direction. Using bottom spray without the tubewith charcoal/zeolite provides a desirable agglomerated particle in themanner of this invention. The lower limit of this process is nominally100 microns.

d. Other fluid bed techniques: There are many other physicalarrangements that are used inside of batch fluid beds to coat oragglomerate particles. Rotating plates or tangential spray arrangementsare examples.

Agglomerators

These are usually mixing devices that could be used to move a mixture ofzeolite and charcoal while a solution of binder is sprayed into themixer. The resulting particles are random mixtures. The particles mayhave to be dried after agglomerating.

Spray Drying

This type of process can increase the size of smaller particles byatomizing with a binder. Mixing ground charcoal with zeolite andspraying will form an agglomerate. However, masking would not beexpected to be good and the resulting particle is small (200 microns).

Prilling

In this approach a large amount of carrier (50%) is used to immobilizethe small zeolite particles. Masking would be expected to be poor.

Extrusion

Co-mixing the charcoal and the zeolite and then extruding into "noodles"using a binder would provide an adherent mixture, but masking would notbe substantially accomplished.

Mechanofusion

In this process there is no binder. Small sized particles aremechanically bonded to a large particle surface. This relatively newtechnique is a low volume, very specialized process.

Taking the foregoing into consideration, using the Wurster process apreferred particle is made using 300-500 micron size carbon (CALGONPCB30x140) and 1-90 micron size intermediate range zeolite (VALFOR;Philadelphia Quartz) with METHOCEL E5 as the binder. This provides thefollowing advantages. Starting with a larger size core particle gives abigger "target" for the coating spray to hit. The particle flow in thedraft tube is probably more regular. Moreover, for the same weightpercent of coating, the wall is thicker on a larger core particle. (Thesurface to area ratio is smaller for a larger particle.) A thicker wallmeans better masking. In addition, METHOCEL E5 is somewhat tacky and hasa high viscosity. While a higher viscosity can limit the ability toatomize and pump-on the coating, it also can mean a stickier coating.Other coatings that are less viscous do not appear to duplicate thiseffect.

EXAMPLE VII

In a representative example, 100 g of METHOCEL 5E (binder) are dissolvedin 1900 ml deionized water. Zeol ite (VALFOR CP300-56; 398 g) is addedto the METHOCEL solution (19.9% dispersion). A high shear mixer (TekmarHigh Shear Mixer Model SD45) is used to create a dispersion of thezeolite. Typical shear time 15 minutes.

996 g. of commercial carbon powder are placed in a Wurster Fluid BedCoater (ca. 10 cm Ascoat Unit Model 101, Lasko Co., Leominster, Mass.).The carbon material is fluidized in the bed at an air flow of 18 scfm(standard cubic ft./min.); the inlet temperature is brought to 138° F.(58.9° C.).

The flow of VALFOR/METHOCEL coating solution into the spray nozzle isbegun (1/4-Round Spray Nozzle made by The Spraying Systems Co.;0.40/0.100 fluid cap.; 0.120 air cap.). The flow rate is set at 7.7g/min. Exit air temperature is 77°-84° F. (25° to 28.9° C.).

In a typical run, particles prepared in the foregoing manner comprise 20to 50% (wt.) carbon; 20 to 40% (wt.) zeolite, the balance comprising thebinder. Particle sizes range from 90 to 300 μ.

As can be seen from the foregoing, the invention herein also providesimproved carbon-containing, zeolite-coated, odor-controlling particlesthat are especially adapted for use in catamenials, especially sanitarynapkins, as well as in other disposable sanitary products. The highlypreferred particles herein are of an off-white to gray or light bluishcolor, and are, thus, rather unobtrusive in the product. Advantageously,the particles herein need not be used in conjunction with what could beirritating or toxicologically-unacceptable antimicrobials, e.g., copperions, antifungals, and the like. Indeed, in one preferred embodiment,the particles herein are substantially free from such antimicrobial andantifungal agents. The use of the particles herein in conjunction withabsorbent gelling materials, as disclosed hereinabove, not only enhancesthe fluid absorbency of the finished product, but also increases odorcontrol properties. While not intending to be limited by theory, itappears that absorbent gelling materials, especially acrylates, mayserve to control ammonia-type odors. Thus, using the zeolite-coatedcarbon particles in simple admixture with particles of absorbent gellingmaterials, preferably substantially in the absence ofantimicrobials/antifungals, yields a desirable level of odor control onboth sanitary napkins and pantiliners. Moreover, the mixture ofzeolite-coated carbon particles and particulate absorbent gellingmaterial (especially polyacrylates or starch/acrylates) is easily addedto disposable articles without resort to, somehow, affixing theparticles to fibers, or meshing the particles in fiber webs, orembedding them into a topsheet, although all such methods can be used,if desired. Rather, the particle mixture can simply be spread orsprinkled onto a water permeable paper or nonwoven tissue and coveredwith a second tissue to form a tissue/particles/tissue laminatestructure that is quite thin. The tissue laminate is then placed in thearticle, generally as a layer directly under the topsheet. (Optionally,an absorbent core can underlie the tissue layer, e.g., in a sanitarynapkin. For pantiliners, the additional fluid absorbent capacityafforded by the absorbent core is optional, and may not be needed formost uses.) The zeolite/carbon particles control odor and the absorbentgelling material both helps control some odor, plus absorbs body fluids.

The following Example VIII illustrates the above points in somewhatgreater detail. In this Example, which illustrates a preferredtissue/particles/tissue laminate and its use in a sanitary napkin orpantiliner, the following preferred materials are used.

1. Carbon--available from Calgon as PCB30x140; average particle size(sieve analysis) ranging from 100 to 600 microns, preferably 200 to 500microns.

2. Zeolite--available as any of the VALFOR series; or Zeolite Y(Conteka); average particle size (x-ray analysis) ranging from 0.2 to 90microns.

3. Coating method--Wurster fluidized bed, using METHOCEL E5/water at 4%to 10%, preferably 4.5% to 8.5%, by weight METHOCEL.

4. Ratio of zeolite:carbon (wt.) from about 0.8 to 1.25, preferably 1:1.

5. Color--off-white to gray or gray/bluish.

6. Size of zeolite/METHOCEL/carbon particle (sieve analysis, averagesize) from about 125 to about 825 microns, although particles up toabout 1,000 microns are satisfactory.

7. Absorbent gelling material--polyacrylate orstarch/polyacrylate/available as L-74 from Shokubai or as 1180 fromNALCO. Average particle sizes range from about 100 to 350 microns,preferably from about 150 to 300 microns.

8. Weight ratio of zeolite-coated carbon particles to absorbent gellingmaterial particles--in the range of 10:1 to 1:10, preferably 3:1 to 1:3,most preferably about 1:1.

9. Amount of zeolite-coated carbon particles used per tissuelaminate--for sanitary napkins ranging from about 0.1 g to about 1.5 g,preferably at least about 0.24 g. For pantiliners, somewhat less can beused; typically from about 0.1 g to about 0.5g.

10. Amount of absorbent gelling material used per tissue laminate--forsanitary napkins ranging from about 0.2 g to about 1.0 g, preferably atleast about 0.5 g. For pantiliners, somewhat less can be used; typicallyfrom about 0.3 g to about 0.5 g.

EXAMPLE VIII

The preparation of a thin sanitary napkin is as follows.

For convenience, a commercially-available trifold wet-laid tissuecontaining approximately 5 g of absorbent gelling material particles persquare foot (which yields approximately 0.68 g absorbent gellingmaterial per sanitary napkin pad) is used to prepare the core. Thetrifold tissue laminate is sprayed with a fine mist of water and openedto expose the absorbent gelling material. 1.2 g of VALFOR-coatedcharcoal, prepared by the Wurster coating process (noted above) issprinkled onto the AGM. The two sides of the tissue are folded back totheir original position, thereby sealing the absorbent gelling materialand zeolite-coated charcoal inside. The still moist core is resealed byusing a hot iron, pressing firmly.

An absorbent core prepared in the foregoing manner (ca. 8.0 in.×2.75in.) is placed on top of a slightly larger piece of polyethylenebacksheet. An additional piece of tissue is positioned on top of thecore. A formed-film topsheet of the type disclosed in U.S. Pat. No.4,463,045 is coated evenly on its underside with ca. 0.03 g of a latexadhesive, and excess adhesive is wiped off. The topsheet is rolled witha glass rod to ensure good contact and proper application of adhesive.The topsheet is then placed on top of the above-prepared core assembly.To ensure good core bonding, the topsheet is weighted with a piece ofplexiglas.

The assembly is sealed together to provide the overallproduct:topsheet/tissue/absorbent core with odor-controllingcomponents/backsheet. Optionally, adhesive can be applied on the outsideof the backsheet of the pad for affixing the article to undergarments.The topsheet of the product is sprayed with about 0.03 g of PEGOSPERSE(PEG200) surfactant to hydrophilize the fluid-receiving surface of thetopsheet.

While the foregoing illustrates the preparation of a sanitary napkin inthe manner of this invention, an entirely similar operation can beemployed to prepare a pantiliner (generally of the dimensionsapproximating 5.4 in.×2 in.) with appropriate modifications of theamounts of the ingredients, as noted hereinabove.

What is claimed is:
 1. A sanitary napkin or pantiliner, comprising afluid-absorbing pad, said pad containing one or more water-wettablefluid-absorbing materials and at least about 0.2 g. of a syntheticzeolite, said zeolite being characterized by an SiO₂ /AlO₂ ratio from 2to 7 , said zeolite being in the protonic, sodium, potassium ammonium oralkylammonium form.
 2. Asanitary napkin or pantiliner according to claim1 wherein said fluid-absorbing pad is interposed between afluid-permeable topsheet and a fluid-impermeable backsheet, saidsanitary napkin or pantiliner containing at least about 0.3 g of saidzeolite.
 3. A sanitary napkin or pantiliner according to claim 2 whichadditionally comprises activated carbon.
 4. A sanitary napkin orpantiliner according to claim 3 which additionally comprises anabsorbent gelling material in said fluid-absorbing pad.